Francesco Rubino

Time​ Magazine

08-05-2025

With obesity medications like Wegovy and Zepbound dominating social media and conversations in doctors' offices, you might think that doctors at least have a good idea about what obesity is. But there really isn't a conclusive definition of the condition, with some clinicians maintaining it's a chronic disease, like high blood pressure or diabetes, while others say it's not a disease itself, but a risk factor for other diseases. 'There isn't a description in medical history, because historically, obesity has been recognized as a spectrum,' says Dr. Francesco Rubino, chair of metabolic and bariatric surgery at King's College London.
In 2024, he led a group of more than 50 international experts, convened by the medical journal the Lancet, in an effort to define obesity so doctors could better recognize, diagnose, and treat it as a disease. 'We found that nobody was entirely right when we started to discuss whether obesity is a disease or not, and also nobody was entirely wrong,' he says.
The committee came up with guidelines, published in January, to help doctors distinguish between preclinical obesity—in which people gain weight but may not yet have any negative health outcomes—and clinical obesity, in which people have symptoms such as diabetes or sleep apnea. It may seem semantic, but defining a condition that affects more than 1 billion people worldwide has consequences for treatment. Rubino says understanding where people fit on the obesity spectrum, and creating more useful distinctions between those at risk and those beginning to experience disease, will help more people to manage their weight better with medical help. Already, 79 major health organizations, including the American Heart Association, the American Diabetes Association and the World Obesity Federation, have endorsed the revised guidelines.